(not applicable)
The invention relates generally to a method and apparatus for storing and playing back digital audio radio signals, and more particularly to a method and apparatus for enabling non-real time as well as real time playback of digital audio radio signals.
Satellite radio operators will soon provide digital quality radio broadcast services covering the entire continental United States. These services will offer approximately 100 channels, of which nearly 50 channels in a typical configuration will provide music with the remaining stations offering news, sports, talk and data channels. Digital radio may also be available in the near future from conventional analog radio broadcasters that will provide a terrestrial based system using signals colocated in the AM and FM bands.
Satellite radio has the ability to improve terrestrial radio""s potential by offering a better audio quality, greater coverage and fewer commercials. Accordingly, in October of 1997, the Federal Communications Commission (FCC) granted two national satellite radio broadcast licenses. The FCC allocated 25 megahertz (MHZ) of the electromagnetic spectrum for satellite digital broadcasting, 12.5 MHz of which are owned by Sirius Satellite Radio and 12.5 MHz of which are owned by the assignee of the present application xe2x80x9cXM Satellite Radio Inc.xe2x80x9d
The system plan for each licensee presently includes transmission of substantially the same program content from two or more geosynchronous or geostationary satellites to both mobile and fixed receivers on the ground. In urban canyons and other high population density areas with limited line-of-sight (LOS) satellite coverage, terrestrial repeaters will broadcast the same program content in order to improve coverage reliability. Some mobile receivers will be capable of simultaneously receiving signals from two satellites and one terrestrial repeater for combined spatial, frequency and time diversity, which provides significant mitigation of multipath interference and addresses reception issues associated with blockage of the satellite signals.
In accordance with XM Satellite Radio""s unique scheme, the 12.5 MHZ band will be split into 6 slots. Four slots will be used for satellite transmission. The remaining two slots will be used for terrestrial reinforcement.
In accordance with the XM frequency plan, each of two geostationary satellites will transmit identical or at least similar program content. The signals transmitted with QPSK modulation from each satellite (hereinafter satellite 1 and satellite 2. For reliable reception, the LOS signals transmitted from satellite 1 are received, reformatted to Multi-Carrier Modulation (MCM) and rebroadcast by terrestrial repeaters. The assigned 12.5 MHZ bandwidth (hereinafter the xe2x80x9cXMxe2x80x9d band) is partitioned into two equal ensembles or program groups A and B. Each ensemble will be transmitted by each satellite on a separate radio frequency (RF) carrier. Each RF carrier supports up to 50 channels of music or data in Time Division Multiplex (TDM) format.
Thus, in a system as described above, a need exists for a device that receives, stores, and plays back digital audio radio signals in a manner that provides the user flexibility and ease of use in choosing between and among various content selections whether such content is live or previously stored. A need further exists for a device that gives the user flexibility in selecting, storing and playing back selections based on the type of content or other user preferences.
In a first aspect of the present invention, a device for receiving, storing and playing back digital audio radio signals comprises a receiver, a decoder, a user input, a storage medium coupled to the decoder, and a system controller coupled to the user input. The receiver receives a digitally encoded bit stream over-the-air on a plurality of communication resources, wherein each of the plurality of communication resources contains content and associated index information. The decoder selectively decodes a selected plurality of communication resources and the user input selects the selected plurality of communication resources based on the associated index information and selects a portion of the content contained in selected plurality of communication resources to be retrieved. The storage medium stores the content and associated index information contained in the selected plurality of communication resources and the system controller stores and retrieves content to and from the storage medium based on input received at the user input.
In another aspect of the present invention, a method of receiving and storing digital audio radio signals, comprises the steps of receiving a digitally encoded bit stream over-the-air on a plurality of communication resources, wherein each of the plurality of communication resources contains content and associated index information and selectively decoding a selected plurality of communication resources. The method then enables the selection of the selected plurality of communication resources using a user input and the associated index information and stores the content and associated index information contained in the selected plurality of communication resources in a memory device.
In a third aspect of the present invention, a system for transmitting, receiving, storing and playing back digital audio radio signals comprises an encoder, a transmitter, a receiver, a decoder, a user input, a storage medium coupled to the decoder, and a system controller coupled to the user input. The encoder encodes a plurality of content sources and associated index information in a digitally encoded bit stream and the transmitter transmits over-the-air the plurality of content sources on a corresponding plurality of communication resources. The receiver receives the digitally encoded bit stream over-the-air on the plurality of communication resources and the decoder selectively decodes a selected plurality of communication resources. The user input selects the selected plurality of communication resources based on the associated index information and selects a portion of the content contained in selected plurality of communication resources to be retrieved. The storage medium stores the content and associated index information contained in the selected plurality of communication resources and the system controller stores and retrieves content to and from the storage medium based on input received at the user input interface.